The present invention relates to an electromagnetic flow meter, and more particularly to an improvement of making the conduit thinner in the detection portion of the electromagnetic flow meter and a flow rate detection correcting device.
The basic configuration of an electromagnetic flow meter is defined in "Flow Rate Measuring Method By Means of an Electromagnetic Flow Meter" JIS, Z8764. The basic configuration shown in FIG. 2 provides for an excitation current I flowing into an excitation coil 21 provided outside a conduit 20 so that a magnetic field B is generated from the end portion of a core 22. Electromotive force generated in the fluid flowing in the conduit 20 is detected by an electrode 23, and the detected electromotive force is converted by a converter 25 into a flow-rate signal. The conduit 20, the excitation coil 21, the electrode 23, and so on, are built in a detector 24.
Generally, such an electromagnetic flow meter is provided in the form of piping. In this case, there is a defect in which the inter-surface distance L (see FIG. 2) of the detector 24 is large causing the weight of the conduit 20 the to increase this in return causes workability of attaching the conduit 20 to the piping to be lowered or; lacing lining on the inner surface of the conduit 20 becomes difficult.
Accordingly, trials to shorten the intersurface distance L have been made and it has been recognized that the inter-surface distance L must be selected so as not to be shorter than 1.3 times as long as the inside diameter D of the conduit 20. This is because if the inter-surface distance L is shortened, the electromotive force becomes low so that the signal-to-noise ratio, that is, S/N, becomes low by being affected by a mate piping. Thus, it has been recognized experientially that the ratio of the inter-surface distance L to the inside diameter D of the conduit must be selected to be 1.3 at the least, and this recognition has become common knowledge. However, nothing having a ratio smaller than 1.3 has been put into practical use.